netdev - Re: [PATCH net-next] inet: restore gso for vxlan

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Date:	Thu, 07 Nov 2013 14:33:06 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH net-next] inet: restore gso for vxlan

On Sun, 2013-10-27 at 18:18 -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> Alexei reported a performance regression on vxlan, caused
> by commit 3347c9602955 "ipv4: gso: make inet_gso_segment() stackable"
> 
> GSO vxlan packets were not properly segmented, adding IP fragments
> while they were not expected.
> 
> Rename 'bool tunnel' to 'bool encap', and add a new boolean
> to express the fact that UDP should be fragmented.
> This fragmentation is triggered by skb->encapsulation being set.
> 
> Remove a "skb->encapsulation = 1" added in above commit,
> as its not needed, as frags inherit skb->frag from original
> GSO skb.
>  
> Reported-by: Alexei Starovoitov <ast@...mgrid.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Tested-by: Alexei Starovoitov <ast@...mgrid.com>
> ---
>  net/ipv4/af_inet.c |   15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index f4a159e705c0..09d78d4a3cff 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -1251,8 +1251,8 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
>  	struct sk_buff *segs = ERR_PTR(-EINVAL);
>  	const struct net_offload *ops;
>  	unsigned int offset = 0;
> +	bool udpfrag, encap;
>  	struct iphdr *iph;
> -	bool tunnel;
>  	int proto;
>  	int nhoff;
>  	int ihl;
> @@ -1290,8 +1290,8 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
>  		goto out;
>  	__skb_pull(skb, ihl);
>  
> -	tunnel = SKB_GSO_CB(skb)->encap_level > 0;
> -	if (tunnel)
> +	encap = SKB_GSO_CB(skb)->encap_level > 0;
> +	if (encap)
>  		features = skb->dev->hw_enc_features & netif_skb_features(skb);
>  	SKB_GSO_CB(skb)->encap_level += ihl;
>  
> @@ -1306,24 +1306,23 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
>  	if (IS_ERR_OR_NULL(segs))
>  		goto out;
>  
> +	udpfrag = !!skb->encapsulation && proto == IPPROTO_UDP;

It seems I did an error here, shouldn't it be

     udpfrag = !skb->encapsulation && proto == IPPROTO_UDP;

instead ?

I am not sure UFO and vxlan are compatable...


>  	skb = segs;
>  	do {
>  		iph = (struct iphdr *)(skb_mac_header(skb) + nhoff);
> -		if (!tunnel && proto == IPPROTO_UDP) {
> +		if (udpfrag) {
>  			iph->id = htons(id);
>  			iph->frag_off = htons(offset >> 3);
>  			if (skb->next != NULL)
>  				iph->frag_off |= htons(IP_MF);
>  			offset += skb->len - nhoff - ihl;
> -		} else  {
> +		} else {
>  			iph->id = htons(id++);
>  		}
>  		iph->tot_len = htons(skb->len - nhoff);
>  		ip_send_check(iph);
> -		if (tunnel) {
> +		if (encap)
>  			skb_reset_inner_headers(skb);
> -			skb->encapsulation = 1;
> -		}
>  		skb->network_header = (u8 *)iph - skb->head;
>  	} while ((skb = skb->next));
>  


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